Cannot browse certain websites

Hope someone can help me. We are running Microsoft DNS on a Server 2008R2 box. Nobody within our organization can visit the site http s : // nppes. cms. hhs. gov/
. However, we can access this site outside of the building from our homes. I've verfied that this traffic not even reaching our web filter, so I know the web filter is not blocking it.

Our internal DNS server is using fowarding to Time Warner dns servers of 209.18.47.61 and 209.18.47.62.

However, if i go onto the NIC of my local computer and statically set my DNS to be these servers, I can load the site fine. Therefore, I'm pretty sure it's ap roblem with our internal DNS but I have no idea how to troubleshoot this.